linux-ext4 - Re: [PATCH][RFC]Ext4: Use get_cpu()/put

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Message-ID: <20071103050137.GE2863@webber.adilger.int>
Date:	Sat, 3 Nov 2007 13:01:37 +0800
From:	Andreas Dilger <adilger@....com>
To:	Mingming Cao <cmm@...ibm.com>
Cc:	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH][RFC]Ext4: Use get_cpu()/put_cpu() in preemptible
	context

On Nov 02, 2007  17:35 -0700, Mingming Cao wrote:
> Index: linux-2.6.24-rc1/fs/ext4/mballoc.c
> ===================================================================
> --- linux-2.6.24-rc1.orig/fs/ext4/mballoc.c	2007-11-02 17:22:18.000000000 -0700
> +++ linux-2.6.24-rc1/fs/ext4/mballoc.c	2007-11-02 17:23:02.000000000 -0700
> @@ -4006,7 +4006,8 @@ static void ext4_mb_group_or_file(struct
>  		return;
>  
>  	BUG_ON(ac->ac_lg != NULL);
> -	ac->ac_lg = &sbi->s_locality_groups[smp_processor_id()];
> +	ac->ac_lg = &sbi->s_locality_groups[get_cpu()];
> +	put_cpu();
>  
>  	/* we're going to use group allocation */
>  	ac->ac_flags |= EXT4_MB_HINT_GROUP_ALLOC;

Shouldn't the put_cpu() be after ac->ac_lg is no longer being used?
I guess there would otherwise be a danger of other processes using
the same s_locality_groups[] struct?

Cheers, Andreas
--
Andreas Dilger
Sr. Software Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

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